I like to make this ultra-simple mousse cake for dinner parties, especially when I'm pressed for time. The cake doesn't take long to put together, and it can chill while I prep the rest of the meal. Since chocolate is the star ingredient here, use the best you can find- it will make all the difference.

Make the Crust:Butter the bottom of a 9 x 3-inch springform pan. In a medium bowl, stir together the cookie crumbs with the melted butter until combined. Pat the crumb mixture onto the bottom of the pan in an even layer. Refrigerate the crust while you make the mousse.

Make the Mousse:Place the chocolate in the bowl of a food processor and process just until finely ground. (Leave the chocolate in the processor.)

In a small saucepan, combine the milk, sugar, espresso powder, and salt and cook over medium heat, stirring frequently, until the sugar dissolves and the milk comes to a boil. With the food processor running, pour the hot milk mixture through the feed tube and process until the chocolate is completely melted. Scrape down the sides of the bowl, add the vanilla extract, and process until blended. Scrape the mixture into a large bowl and let cool.

In the bowl of an electric mixer, using the whisk attachment, beat the heavy cream at high speed until soft peaks form. Using a rubber spatula, gently fold one-third of the whipped cream into the chocolate mixture. Fold in the remaining cream until completely blended.

Scrape the mousse onto the crust and spread it into an even layer. Refrigerate the cake for at least 3 hours.

Unmold the Cake:Run a sharp thin-bladed knife under hot water and wipe dry, then run the knife between the cake and the side of the pan to release the cake; reheat the knife as necessary. Remove the side of the springform pan. If necessary, run a small metal spatula around the side of the cake to smooth any rough patches.

To serve, slice the cake with a hot knife, wiping it clean between each cut. Serve each slice topped with a dollop of whipped cream and a sprinkle of wafer crumbs.

In the chilled bowl of an electric mixer, using the whisk attachment, whip 1 1/2 cups heavy cream at high speed just until it begins to thicken. Add 3 tablespoons confectioners' sugar (sifted) and 1 1/2 teaspoons vanilla extract and beat until soft peaks form. Use immediately, or cover and refrigerate.